As a functional material such as a photonics, electronic, chemical, or biological material, an organic-inorganic hybrid material has been actively developed recently.
There are some proposed synthetic methods of an organic-inorganic hybrid material. For example, intercalation of an organic polar molecule into a layer-structured inorganic compound is known. By using this method, there are proposed applications such as an application to a photonic memory material or an excimer-fluorescent coating material (refer to Patent Document 1) and an application to an organic EL device (non-Patent Document 1).
[Patent Document 1]
    Japanese Patent Laid-Open No. 11-263615[Non-Patent Document 1]    M. Era, et al., Applied Physics Letters, vol. 65, No. 8, 676-678 (1994)
Further, sol-gel method has drawn particular attention as a synthetic method of an organic-inorganic hybrid material. The sol-gel method is one kind of chemical reactions, in which a solid is prepared by a liquid phase reaction, and is a synthetic method, in which a state (sol) where colloid is stable with sufficient fluidity is prepared to make a transition to a solid state (gel) that does not have the fluidity any more by evaporating a solvent and the like. As for details of the sol-gel method like this, knowledge can be obtained from a lot of publications (for example, refer to Non-Patent Document 2). In addition, the sol-gel method has been already put into practical use nowadays as a manufacturing process for various coating films and bulk bodies while attracting attention originally as a technique for manufacturing glass (refer to Non-Patent Document 3).
[Non-Patent Document 2]
    Sumio Sakka, “Science of Sol-Gel Method”, Agune Shouhuu, Tokyo, 4-8 (1988)[Non-Patent Document 3]    Sumio Sakka, Ceramics, vol. 37, No. 3, 136-142 (2002)
Then, when a state of dried gel that can be obtained by this sol-gel method is used as a final product, an organic-inorganic hybrid material into which a heat-sensitive organic group or organic compound (that is, an organic moiety) is introduced can be easily synthesized with heat treatment at low temperatures from 100 to 200° C. In other words, being able to form an inorganic matrix (in particular, an oxide matrix) at low temperatures can be said to be one of advantages of the sol-gel method in synthesizing an organic-inorganic hybrid material.
Now, in the case of synthesizing an organic-inorganic hybrid material by the sol-gel method, miscibility between an inorganic matrix and an organic moiety is important. Stated another way, in order for the organic moiety not to condense to cause a phase separation, it is required that some sort of interaction is given between the inorganic matrix and the organic moiety to disperse uniformly.
As a method for that purpose, it is generally accepted that organosilicate is used to make organic-inorganic hybrid. The organosilicate is silicate that has an organic group partially substituted for an alkoxyl group, which is typified by polydimethyl siloxane. Since an organic-inorganic hybrid material in which an inorganic matrix and an organic moiety are bonded (have interaction) through a covalent bond can be synthesized by hydrolysis and polycondensation of the organosilicate like this, a phenomenon such as the foregoing phase separation is not caused.
An organic-inorganic hybrid material that can be the organosilicate like this has characteristics of an inorganic compound such as great heat resistance and characteristics of an organic compound such as flexibility in combination. For example, an organic-inorganic hybrid material that has such properties as rubber and great heat resistance is synthesized by using polydimethyl siloxane (refer to Non-Patent Document 4). Further, there are applications such as an application to a sliding member (refer to Patent Document 2).
[Non-Patent Document 4]
    Noriko Yamada, et al., Journal of Materials Chemistry, vol. 7, No. 8, 1491-1495 (1997)[Patent Document 2]    Japanese Patent Laid-Open No. 2002-212422
In addition, there is an organic-inorganic hybrid material synthesized by sol-gel method while an organic compound is further added to organosilicate. In this case also, a phase separation can be avoided by giving an interaction such as π-π stacking between an organic group of the organosilicate and the added organic compound, which is efficient. As applications, an application to a colored glass bottle by adding a pigment (refer to Non-Patent Document 5) and an application to an organic EL device by adding a light-emitter (refer to Non-Patent Documents 6 and 7 and Patent Documents 3 and 4) are considered, which also can be said to have high mechanical strength and durability of an inorganic compound and various optical properties (absorption and luminescence properties) of an organic compound in combination.
[Non-Patent Document 5]
    Organic-Inorganic Hybrid Material (Technical Data Collections) (Technical Information Institute Co., Ltd.), 208-215[Non-Patent Document 6]    Tony Dantas de Morais, et al., Advanced Materials, vol. 11, No. 2, 107-112 (1999)[Non-Patent Document 7]    Monika Schneider, et al., Advanced Materials, vol. 12, No. 5, 351-354 (2000)[Patent Document 3]    Japanese Patent Laid-Open No. 9-279135[Patent Document 4]    Japanese Patent Laid-Open No. 2000-306669
As described above, by using organosilicate, an organic-inorganic hybrid material that has a silica matrix and has characteristics of organic compound and inorganic compound in combination can be synthesized. However, it is a matter of course that these methods can be only applied to an organic-inorganic hybrid material that has a silica matrix.
A lot of metal oxides exist, which are superior in aspects such as durability, heat resistance, and mechanical characteristics. Further, sol-gel method using silicate needs an acid or an alkali basically and takes a long time to galate completely, which is not useful for a process either. Consequently, it is important to discover a method of synthesizing an organic-inorganic hybrid material that has a metal oxide matrix other than silica matrix.
A method itself of manufacturing not an organic-inorganic hybrid material but simply a metal oxide by so-gel method is well known, where it is often the case that a metal alkoxide is used as a starting material. This case has an advantage that an acid or alkali is unnecessary unlike silicate. However, since a metal alkoxide has a fairly quick rate of hydrolysis (refer to Non-Patent Document 8), it is a drawback to generate precipitation such as a hydroxide or an oxide as soon as water for hydrolysis and polycondensation is added, with the result that it is not possible to prepare stable sol.
[Non-Patent Document 8]
    Jianye Wen, et al., Chemistry of Materials, No. 8, 1667-1681 (1996)
In order to overcome this, it is necessary to make a reaction rate of hydrolysis slower. As a well-known method, a chemical modification (for example, chelate stabilization) is kwon (refer to Non-Patent Document 9), which prevents a rapid formation of a network due to hydrolysis by partially substituting a β-diketone, an alkanol amine, or the like for an alkoxyl group of a metal alkoxide. According to the chemical modification like this, a coating film of a metal oxide material such as zirconia that has a superior strength can be formed by sol-gel method (refer to Patent Document 5).
[Non-Patent Document 9]
    C. Sanches, et al., Journal of Non-Crystalline Solids, vol. 100, 65-76 (1998)[Patent Document 5]    Japanese Patent Laid-Open No. 10-259095
In addition, there is also an example where a property of a coordinating β-diketone is applied to patterning of a metal oxide (refer to Non-Patent Document 10 and Patent Document 6). In other words, since a chelating β-diketone absorbs light in an ultraviolet region and becomes easily-removable by irradiating ultraviolet corresponding to the absorption, by irradiating ultraviolet after coating sol stabilized with a β-diketone, hydrolysis and polycondensation progress only in the irradiated portion to galate easily. Then, patterning becomes possible since a region that is not irradiated, which does not gelate, can be washed away with a solvent.
[Non-Patent Document 10]
    Katsuhide Shinmou, et al., Japanese Journal of Applied Physics, vol. 33, No. 8B, L1181-L1184 (1994)[Patent Document 6]    Japanese Patent No. 3343377
However, all of these reports are methods for preparing a metal oxide by so-gel method, which are not a report on a synthesis of an organic-inorganic hybrid material that has a metal oxide matrix.
As described above, most of organic-inorganic hybrid materials have a silica matrix while there are few that have a metal oxide matrix. It is possible to just prepare sol in which a metal alkoxide and some sort of organic compound are dissolved in the same solvent to synthesize an organic-inorganic hybrid material by sol-gel method. However, the above-mentioned problem with respect to miscibility comes out since a metal oxide matrix in this case eventually has no organic group. Therefore, an organic-inorganic hybrid material in which an organic group is directly connected to a metal oxide matrix is required.
Further, even in the chemical modification (chelate stabilization) using a β-diketone, which is reported in the above-mentioned Non-Patent Document 10 and Patent Document 6, the β-diketone is added to stabilize sol, which is eventually desorbed by calcination or irradiation of ultraviolet. In other words, it is not possible to realize an organic-inorganic hybrid material that develops a different function from a mere metal oxide by remaining directly connected to a metal oxide matrix.
Consequently, it is an object of the present invention to provide an organic-inorganic hybrid material that has an organic group directly connected to a metal oxide. In particular, it is an object thereof to provide a functional organic-inorganic hybrid material in which an organic group directly connected to a metal oxide develops a coloring property, a light-emitting property, or semiconductivity.
In addition, it is an object of the present invention to provide a material (a composition for coating application) for synthesizing an organic-inorganic hybrid material according to the present invention. Further, it is an object thereof to provide a method of using the composition for coating application to manufacture an organic-inorganic hybrid material according to the present invention.